You can also non-isometrically scale most shapes in this dialog. Some shapes will have to be ungrouped first (then you can regroup them later). You can group/ungroup shapes by selecting them, then [menu bar --> Edit --> Grouping/Merging --> ...].

Finally, and this is probably the easiest for you, you can directly add rectangles to the scene with the primitive shape dialog.

We hope in a future version to also offer non-isometric scaling for whole models. But this is a tricky task ;)